Early Season Growth and Photosynthesis of Intraspecific Cotton Hybrids

Randy Wells and William R. Meredith, Jr.


 
ABSTRACT

Experiments were performed to determine what differences exist in growth and canopy photosynthesis among intraspecific hybrids and their parents. Earlier published results (Crop Sci. 26:1119, 1986) indicated that heterosis was exhibited by early season relative growth rate, relative leaf area growth rate, net assimilation rate, and crop growth rate. The hybrids, however, did not exhibit alterations in the relative partitioning patterns of dry matter (e.g. leaf area vs. plant dry weight). These early growth advantages displayed by the hybrids contributed to the 29 and 32% greater maximal observed leaf area and plant dry weight of the hybrids as compared to their parents. Subsequent experiments were designed to determine the relationship between leaf area production and canopy photosynthesis.

Seedling photosynthesis and its relationship to early growth was observed in four environments (2 years with 2 planting dates each). Measurements were made within a row with a 1 m long X 25 cm wide Mylar covered chamber. Carbon dioxide concentration changes were monitored with a closed photosynthesis system (LiCor, Inc., Lincoln, NE) which utilizes ambient environmental conditions (CO2 concentration, relative humidity, temperature and light).

Either the hybrid's total canopy leaf area or leaf area/plant was greater than their parents (significant at the 0.10 level or better) in three of four environments. Photosynthesis of the seedling canopy was significantly correlated with the leaf area within the chamber, with correlation coefficients of 0.57**, 0.67**, 0.67** and 0.80** for the four environments. Similarly, there was a significant relationship between leaf area/plant and photosynthesis/plant with correlation coefficients of 0.74**, 0.77**, 0.70** and 0.83** for the four environments. Single leaf photosynthetic efficiency, however, was not different due to genotype. The data indicate that larger leaf area during seedling growth results in greater photosynthesis on both a canopy and individual plant basis. It appears possible to utilize seedling leaf area and/or seedling dry matter production as determinants of growth potential.



Reprinted from 1987 Proceedings: Beltwide Cotton Production Research Conferences pg. 86
©National Cotton Council, Memphis TN

[Main TOC] | [TOC] | [TOC by Section] | [Search] | [Help]
Previous Page [Previous] [Next] Next Page
 
Document last modified Sunday, Dec 6 1998